Cognitive profiles and rehabilitation of children with developmental and acquired deficits

Within the field of Developmental Neuropsychology I'm studying how does deficits in sensory-motor domains occurring at different developmental stages affect cognitive processes.

I am particularly interested in Cerebral Palsy, a group of permanent disorders of the development of movement and posture, causing activity limitation, that are attributed to non-progressive disturbances that occurred in the developing fetal or infant brain (Rosenbaum et al., 2007).

Motor impairments are the main feature of CP, so that, depending on which body part is more affected, it is distinguished into Hemiplegic (upper limbs), Diplegic (lower limbs) or Tetraplegic (both upper and lower limbs) cerebral palsy. Children with CP frequently present with brain damages affecting cortical and subcortical structures that subserve visual cognition, thus common clinical correlates include limitations in neurovisual functions.

Thus, as they develop, children with CP present limitations in motor competence and neurovisual functions, which might affect the development of higher-level cognitive processes. Recent evidence indicates a largely shared neural substrate for action performance and imagery (Jeannerod, 2006). A series of studies by Kosslyn (1994, Moulton and Kosslyn, 2009) also provides compelling evidence for an embodied nature of visual imagery, arguing that visual imagery is a kind of ‘simulation’ that relies on perceptual representations and recruits the perceptual brain systems. Therefore, the ability to mentally manipulate visual information might also be affected by early damage to the nervous system. However, this issue has been rarely investigated in children with development disorders.

• Visuo-spatial working memory and mental imagery

In this paper, we adopted the conceptual framework of Cornoldi et al. (2000) of an Active and Passive component of working memory to study visuospatial working memory and visual imagery in a child with Cerebral Palsy.

Beyond a moderate impairment of visuomotor integration skills, cognitive level and memory span, poor performance emerged in figures reconstruction, in memorizing matrix patterns and movements along a path. No such deficits were observed in recalling figures and their positions on a grid and learning groups of words using a visual imagery strategy.

This case highlights that impaired action execution impairs performance in imagery tasks as well, but not when alternative strategies (e.g., verbal encoding) can be adopted.

Results are discussed considering recent evidence on working memory and visual imagery links, and their role in motor rehabilitation training.

• Neurovisual functions

A number of studies have shown the impact that damages to the developing brain exert on visual functions. A timely evaluation of visual functions in children with neurodevelopmental disorders is essential for the definition of rehabilitative intervention tailored on their dysfunctions. Additionally, of particular interest is the follow-up testing of their neurovisual development. This should be routinely conducted (even if vision is not their primary concern) also considering the different timecourses that the vision-for-perception and vision-for-action systems follow.

The article illustrates the results of the application of the ABCDEFV battery ('Atkinson Battery for Child Development for Examining functional vision', Atkinson, Anker, Rae, et al., 2002) for the assessment of children with neurodevelopmental disorders in outpatient setting. The battery has been developed as a screening tool for the identification of vision problems or their precursors in typically developing children. Here, it has been used as an assessment protocol in children already believed to have vision problems, which need to be determined for clinical management and rehabilitation, as in follow-up.

A total of 90 patients underwent a comprehensive evaluation. Subgroups of participants presented similar profiles of impairments with spared basic visuocognitive abilities and limitations in visuoperceptual and visuospatial domains.

The Atkinson’s battery proved to be valuable for evaluation in outpatient setting and follow-up testing. Some limitations emerged. For the definition of personalized and detailed rehabilitation programs a breakdown of the different components of vision and subsequent in-depth evaluation are needed.

• Optic Aphasia

In this paper we reported the case of a girl presenting with Optic Aphasia following Traumatic Brain Injury. Both neurocognitive and language functions were eveluated, and follow-up testing was administered 2 years post-injury to track the evolution of the syndrome. The patient cannot name visually presented objects, but can describe or demonstrate the use of the same objects she cannot name, or sort them into their appropriate categories. The impairment was specific to visual namming, as recognition through modalities different from vision was adeguate (e.g. by touching the object, hearing its sound or being provided with verbal definition of it).

This study and follow-up testing illustrated the evolution of the deficit, from a visual agnosic impairment to the co-occurrence of partial deficit of visual naming of objects and letters (optic aphasia and alexia).

We suggest that such patient presents with mild pre-semantic deficit (in mapping visual information with semantics) as well as post-semantic impairments (in the association between semantics and lexical label). Such performance can be accommodated within Farah’s formulation which implies superadditive mild damage at several stages of object recognition naming model.

• Spatial memory, egocentric/allocentric representations of space

Spatial memory is supported by multiple parallel representations of the environment.

Egocentric perspective (body-centered) and allocentric representations (object-centered) are integrated to allow correct interaction with the world.

According to Milner and Goodale (1995, 2008), the action-related dorsal system is specialized for location of objects in space and visuo-motor integration, and uses an egocentric frame of reference. The perception-related ventral system is specialized for categorical recognition of objects and forms, and supports an allocentric frame of reference.

Here we use a Distance Judgment Task to explore the use of different spatial frames in children with Cerebral Palsy. Following the dorsal stream vulnerability hypothesis (Atkinson et al., 2007) children with cerebral palsy might have more difficulties in egocentric judgments and in the processing of peri-personal space than controls.

Results showed no significant difference between children with cerebral palsy and controls in allocentric judgments, whereas performance was worse in egocentric judgment, indicating inefficient use of body-centered representations.